Water hammer prevention valve and method

ABSTRACT

A valve for preventing water hammer includes a speed reduction device for reducing a speed at which the valve may be closed. A method of preventing water hammer includes closing a valve at a fire hydrant after extracting water from the fire hydrant, in which the valve comprising a speed reduction device that increases an amount of time needed for closing the valve, and operating the valve to close the valve comprises operating the speed reduction device.

RELATED APPLICATIONS

The present application is a Continuation-in-Part of U.S. applicationSer. No. 12/685,823, filed: Jan. 12, 2010

BACKGROUND

Fire hydrants are provided at various points on major water systems asan access to the water in the system. Fire hydrants are so named becausethey are frequently used to access water for fighting fires. However,fire hydrants are also commonly used to access water for other purposes,most notably, construction and irrigation.

Consequently, a wide variety of personnel with different levels oftraining regarding water systems may be using a fire hydrant to getwater for a variety of purposes. In many non-emergency situations, thehydrant may be connected by hose to a water truck that is then filledwith water from the hydrant for transportation to a construction site orother location where the water is needed.

The water in a major water system and available at a fire hydrant istypically under high pressure. This water pressure, if not handledproperly, can cause significant damage to the fire hydrant, the watersystem infrastructure and/or surrounding property. Therefore, it isimportant that personnel using a fire hydrant, regardless of their levelof training, do so properly.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of theprinciples described herein and are a part of the specification. Theillustrated embodiments are merely examples and do not limit the scopeof the claims.

FIG. 1 is a cross-sectional view of a fire hydrant with which theprinciples described herein may be practiced.

FIG. 2 is an illustration of a valve for use with a fire hydrantaccording to principles described herein.

FIG. 3 is an illustration of one particular embodiment of the valveshown in FIG. 2.

FIG. 4 is a further illustration of the gear train illustrated in thevalve of FIG. 3.

FIG. 5A is an illustration of a top view looking down on a valveaccording to another embodiment of the valve of FIG. 2 and theprinciples described herein.

FIGS. 5B and 5C are illustrations of cross-sectional views of the valveshown in FIG. 5A.

FIG. 6 is a flowchart illustrating a method for water hammer preventionaccording to principles described herein.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

The following specification describes a novel valve and associatedmethods for making such a valve and for using the valve with a firehydrant, where the valve limits the speed with which a hydrant user canclose the valve. This generally avoids a problem known as water hammerthat will be described below and which is responsible for much of thedamage possible when misusing a fire hydrant.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present systems and methods. It will be apparent,however, to one skilled in the art that the present systems and methodsmay be practiced without these specific details. Reference in thespecification to “an embodiment,” “an example” or similar language meansthat a particular feature, structure, or characteristic described inconnection with the embodiment or example is included in at least thatone embodiment, but not necessarily in other embodiments. The variousinstances of the phrase “in one embodiment” or similar phrases invarious places in the specification are not necessarily all referring tothe same embodiment.

FIG. 1 illustrates the interior of a fire hydrant (100). As shown inFIG. 1, the fire hydrant (100) includes a lower standpipe (101) thatextends from above the surface into the ground. At the bottom of thelower standpipe (101) is a drain (102) that connects the lower standpipewith an elbow (104). The elbow (104) is connected to the water system(108) serviced by the first hydrant (100).

The drain (102) includes a main hydrant valve (103) that can be openedto allow water from the water system (108) into the hydrant (100). Asnoted above, this water will typically be at a high pressure. The mainhydrant valve (103) is operated by turning a valve stem (105).

The lower standpipe (101) is topped by a barrel (106) which is the mainbody of the hydrant above ground. The barrel includes at least one,typically two and sometimes three, pumper nozzles (108) from which wateris extracted from the hydrant (100). At the end of each nozzle (108),threads are provided by which a valve or hose can be attached to thenozzle (108). Each nozzle (108) is usually covered by a protective cap(109) when not in use.

The valve stem (105) extends from the main hydrant valve (103) throughthe lower standpipe (101) and barrel (106) to connect to an operatingnut (107) at the top of the hydrant (100). This operating nut (107) isturned to drive the valve stem (105) so as to either open or close themain hydrant valve (103) at the drain (102).

The typical operation of a fire hydrant for non-emergency purposes mightbe as follows. Prior to opening the main hydrant valve (103), theprotective cap (109) is removed from a nozzle (108) and a separate valveis attached to the nozzle (108). That valve may, in turn, be connectedto a hose that feeds the tank of a water truck. With this valve in placeon the nozzle (108) and closed, the operating nut (107) is driven toopen the main hydrant valve (103) and charge the hydrant (100) withwater. Water is then extracted from the hydrant (100) by opening andclosing the valve on the nozzle (108).

A common misuse of a fire hydrant occurs when closing either the valveon the nozzle or the main hydrant valve (103). Because the water in thehydrant (100) is at such high pressure, if the flow is interrupted tooquickly, damage can result. Thus, if any valve in the system is closedtoo quickly when water is flowing, a phenomenon known as water hammermay result.

Water hammer is described as follows. When a valve on the hydrant (100)is closed relatively quickly, the momentum of the flowing water hits thenow-closed valve with enough force to rebound in the opposite directionback into the water system. This rebounding volume of water willmomentarily counter the pressure and flow of water still upstream in thesystem. However, the pressure in the system will eventually overcome themotion of the water rebounding from the closed valve and will again slamthat water against the closed valve. That volume of water then rebounds,again, from against the closed valve and the process repeats itselfmultiple times. This repeated slamming of a volume of water against theclosed valve is why the problem is referred to as water hammer.

Water hammer can produce water pressures many multiples in excess of thestandard pressure in the water system. For example, if the water systemhas a static pressure of 100 lbs. per square inch, a water hammer mayproduce pressures as great as eight or nine times this pressure. Giventhis high level pressure involved, water hammer can easily cause damageto the water system infrastructure, such as the water main feeding thehydrant, the hydrant (100) itself, or any equipment connected to thehydrant (100). Additionally, if the water hammer damages the watersystem, the hydrant or any of its connections enough to cause a leak,there may be significant water damage to surrounding property as well asthe inconvenience of having to shut off at least a portion of the watersystem for repairs.

Water hammer and its associated problems are generally avoided if careis taken to close any valve at the hydrant (100) relatively slowly. Ifthe valve, either the main hydrant valve (103) or a valve at the hydrantpumper nozzle (108), is closed slowly enough, the flow of water isgradually diminished and never strikes the closed or closing valve withenough force to rebound back into the oncoming flow of water therebyinitiating a water hammer.

While simple in theory, it is a routine and long-standing problem in theoperation of all water systems that valves at fire hydrants get closedtoo abruptly and water hammer damage results. Untrained personnel whomay be in a hurry for any number of reasons may close off a hydrantvalve too quickly without being aware of the dangers involved.Additionally, even highly-trained water system personnel may sometimes,when in a hurry or concerned with other issues, close a hydrant valvetoo quickly and initiate a water hammer.

Water hammer is of more particular concern with regard to a valveconnected to a pumper nozzle (108). This is true because such valves areusually designed to be closed quickly, if desired, and are usuallyoperated by personnel with little or no water system training.

In light of these issues, the present specification describes a novelvalve and an associated method for use with a fire hydrant that limitsthe speed with which a hydrant user can close the valve. This willgenerally prevent the unwanted initiation of a water hammer and anyconsequent damage to the system or surrounding property. As will beappreciated, however, by those skilled in the art, the principlesdescribed herein may also be integrated into a fire hydrant design aswell as being implemented in a separate valve for connection to a firehydrant nozzle.

FIG. 2 illustrates a hydrant valve, according to principles disclosedherein, that prevents the dangers of water hammer. The valve (200) shownin FIG. 2 may be configured for attachment to the pumper nozzle (108,FIG. 1) of a fire hydrant (100, FIG. 1) to regulate the flow of waterfrom the hydrant.

For this purpose, a channel (205) through the valve (200) has threads(206) on either end. One such set of threads (206) may be sized formating with the threads on a pumper nozzle (108, FIG. 1) of a firehydrant (100, FIG. 1) so that the valve (200) can be mounted on andregulate water flow from the nozzle (108, FIG. 1). The threads on theother side of the channel (205) may be used to attach a hose to thevalve (200). As described above, such a hose may be used to connect thehydrant to a water truck.

The valve illustrated in FIG. 2 is gate valve. However, it will beunderstood by those skilled in the art that the principles describedherein could be implemented with other types of valves including abutterfly or ball valve. As used herein and in the appended claims, theterm “closure mechanism” will refer to the mechanism in each valve thecloses the valve, for example, a gate and worm gear in a gate valve, thebutterfly member in a butterfly valve or the ball in a ball valve.

As shown in FIG. 2, the flow of water through the channel (205) of thevalve (200) is regulated by the gate (204) which moves in and out of thechannel (205) to limit or block the flow of water through the valve(200). The gate (204) is raised and lowered, extended and withdrawn, inand out of the channel (205) by operation of the valve handle (201).

The valve handle (201) is rotated to turn a shaft (203). The shaft (203)is connected to, or includes, a screw (202) that acts as a worm gear tomove the gate (204) in and out of the channel (204).

In a typical valve, the handle (201) is designed for easy and,therefore, quick operation. Consequently, the gate (204) could belowered and the valve (200) completed shut in a relatively short amountof time. As described above, this can result in water hammer. However,in the illustrated valve (200), a speed reduction device (210) isinterposed between the operation of the handle (201) and the gate (204)to limit the speed with which the valve can be closed.

This speed reduction device (210) may be provided according to any ofseveral embodiments which will be described below. Two or more of theseembodiments may also be used together in the same valve (200) toconstitute the speed reduction device (210).

As shown in FIG. 3, a gear train (300) may be interposed between thehandle (201) and the gate (204) so as to limit the speed with which thegate (204) can be closed. The gear train (300) may comprise two or moregears that are driven by the rotation of the handle (201) and, in turn,translate the gate (204) between its open and closed positions. Thegears of the train (300) have a gear ratio such that a larger number ofturns of the handle (201) are required to close the gate (204) thanwould be the case without the gear train (300). Consequently, even ifthe handle (201) is turned very rapidly by an imprudent operator, thegate (204) will move more slowly to close.

A specific example of the gear train (300) is illustrated in FIG. 4. Asshown in FIG. 4, for example, the gear train (300) comprises two gears(401, 402) of different sizes. The handle (201) of the valve is used toturn the shaft (203) which, in turn, rotates a small gear (401). Thissmall gear (401) is meshed with and drives a significantly larger gear(402). The larger gear (402) drives the screw (202) or worm gear,described above, that actually translates the gate (204) of the valveinto and out of the channel

Because of the difference in size, the gear ratio, between the smallgear (401) and the larger gear (402), it will take multiple completeturns of the handle (201) to rotate the larger gear (402) and the screw(202) through a single turn. This can be explained further as follows.Absent the gear train, each complete revolution of the handle producesone complete revolution of the screw (202) and consequent lateraltranslation of the gate (204). With the gear train (300) in place, eachcomplete revolution of the handle (201) produces a complete revolutionof the small gear (401), but only a fraction of a revolution of thelarger gear (402). Thus, the handle (201) and the small gear (401) mustbe completely rotated some number of times greater than one in order toproduce one single revolution of the larger gear (402). It will beappreciated by those skilled in the art that the relative sizes of thegears (401, 402) can be varied and selected depending on how many turnsof the handle (201) are desired to result in one complete turn of thescrew (202).

By thus multiplying the number of turns required of the handle (201) inorder to turn the screw (202) and translate the gate (204), the valvenecessarily requires more time to open or close, even if the handle(201) is being turned quickly. The gear ratio of the gear train (300)can be chosen to prevent even the fastest expected rotation of thehandle (201) from translating into movement of the gate (204) quicklyenough to cause water hammer. As a result, the gear train (300)necessarily prevents an imprudent operator from initiating a waterhammer.

Almost universally, the threads on screws and valves are set such that arightward or clockwise rotation closes the valve or drives the screwwhere as a leftward or counter-clockwise rotation opens the valve toextracts the screw. Hence, the common maxim, “righty tighty, leftyloosey.”

However, because of the gear train (300), the rotation of the handle(201) and the gear (401) will be reversed by the gear (402) in drivingthe screw (202). This will result in an operation contrary to what wouldnormally be expected, i.e., that a rightward or clockwise rotation willopen the valve and a leftward or counter-clockwise rotation will closethe valve.

To avoid this, the threads (206) of the screw (202) may be reversed fromthe standard direction. The result is that the change in rotationdirection caused by the gear train (300) is negated such that arightward or clockwise rotation of the handle (201) will close the gate(204) and a leftward or counter-clockwise rotation of the handle (201)will open the gate (204).

FIG. 5 illustrates another embodiment of the speed reduction device(210). As described here, FIG. 5 includes cross sectional views of aninterface between the shaft (203) and the screw (202) of the valve asdescribed above with respect to FIG. 2. As shown in FIG. 5, the speedreduction device (210) may take the form of a torque control.

FIG. 5A shows a top view of a novel valve 200 as it would appear lookingdown toward the valve handle (201). The cross-sectional views describedbelow and shown in FIGS. 5B and 5C are taken along the line in FIG. 5Alabeled “5B, 5C.”

Referring to FIGS. 5B and 5C, in this embodiment, the shaft (203-1),extending from the handle of the valve, is received in a hollow portionof the screw (202-1). As described above, rotation of the screw (202-1)translates the gate or other closure mechanism of the valve.

In order for the shaft (203-1), which is turned by the handle (201, FIG.2), to drive the screw (202-1) and operate the valve (200, FIG. 2), theshaft (203-1) must be coupled to the screw (202-1). This coupling ismade by a bearing (501) that is biased into a receiving notch (503) ofthe shaft (203-1).

As shown in FIG. 5A, the bearing (501) and a biasing member (502), suchas a spring, are part of the screw (202-1). Consequently, the shaft(203-1) and screw (202-1) are coupled when the bearing (501) is forcedby a bias, such as a spring (502), into the receiving notch (503) of theshaft (203-1). When this is the case, rotation of the shaft (203-1), asindicated by arrow A, will also result in rotation of the screw (202-1),as indicate by arrow B. Thus, the shaft (203-1) can be used to drive thescrew (202-1) and thereby close the valve (200, FIG. 2).

However, if too much torque is applied to the shaft (203-1), which mayoccur if an imprudent operator is attempting to close the valve tooquickly, the bias of the spring (502) will be overcome thereby allowingthe bearing (501) to move out of the receiving notch (503) in the shaft(203-1). This state is illustrated in FIG. 5B.

When the bearing (501) is no longer in the receiving notch (503), thereis no coupling between the shaft (203-1) and the screw (202-1).Consequently, the shaft (203-1) rotates within the hollow portion of thescrew (202-1) without turning the screw (202-1). This continues untilthe shaft (203-1) has been rotated to where the bearing (501) can againbe received in the receiving notch (503) of the shaft (203-1). The shaft(203-1) and screw (202-1) are then re-coupled, according to theconfiguration of FIG. 5A, and the shaft (203-1) can again be used todrive the screw (202-1), unless too much torque is again applied to theshaft (203-1) thereby breaking the coupling between shaft (203-1) andscrew (202-1), as shown in FIG. 5B.

In this way, the shaft (202-1) can only be used to drive the screw(203-1) and operate the valve if the torque used to rotate the shaft(202-1) remains below a certain level. The strength or spring constantof the biasing member (502) can be chosen such that the coupling betweenthe shaft (202-1) and screw (203-1) will remain engaged so long as thevalve is only operated at a sufficiently slow speed and torque so as toreduce or eliminate the dangers of water hammer. If an imprudentoperator attempts to apply more torque and close the valve more quickly,the coupling between the shaft (202-1) and screw (203-1) will be brokenand the valve will not move toward closure until the coupling isrestored and maintained by slower, more gentle rotation of the shaft(202-1).

The valves described herein (e.g., FIG. 2) may be embodied as separatevalves that are selectively attached to the nozzles of a fire hydrant.Alternatively, the valves described herein may be integrated into thepumper nozzles of a fire hydrant. The principles and mechanismsdescribed herein may also be used to control how quickly the main valve(103, FIG. 1) of the hydrant (100, FIG. 1) can be closed.

In any of the valves described herein, an indicator may also be added tothe valve that shows a valve operator the relative open/closed positionof the valve. Consequently, even though the vale may be opening orclosing more slowly than expected, the progress in opening or closingthe valve is shown to the operator by the indicator.

FIG. 6 is a flowchart illustrating a method for water hammer preventionaccording to principles described herein. As shown in FIG. 6, theillustrative method shown is for extracting water from a fire hydrantusing a valve attached to a nozzle of the hydrant.

First, if not already connected or integrated into the hydrant, a valveis connected to a nozzle of the hydrant (step 700). The hydrant can thenbe charged with water (step 701) by opening the main hydrant valve (103,FIG. 1).

Once the valve is in place and the hydrant is charged, the valve can beopened (step 702) to extract water from the hydrant. As described above,water may be extracted, for example, to fill a tanker for construction,fire fighting, irrigation or any of a number of other purposes. With thevalve open, water is extracted from the hydrant (step 703).

When the need for water has been filled (determination 704), whateverthat need is, the valve can be closed to discontinue the flow of water.As described in detail above, if the valve is closed too quickly, waterhammer may occur and potentially damage the water system infrastructure,the hydrant, equipment connected to the hydrant and/or surroundingproperty.

When it is time to close the valve (determination 704), the closuremechanism of the valve is operated (step 705). This may be a valve gate,butterfly member or ball member, depending on the type of valve beingused.

As described herein, a speed reduction mechanism is operated when theclosure mechanism of the valve is operated (step 706). This speedreduction mechanism will limit how quickly the valve can be closed andincrease the time required to close the valve to prevent water hammer.As described above, the speed reduction mechanism will incorporate oneor more devices such as a gear train or a torque control/slippage devicethat will limit how quickly the valve can be closed and increase thetime required to close the valve to prevent water hammer.

The preceding description has been presented only to illustrate anddescribe embodiments and examples of the principles described. Thisdescription is not intended to be exhaustive or to limit theseprinciples to any precise form disclosed. Many modifications andvariations are possible in light of the above teaching.

What is claimed is:
 1. A valve for preventing water hammer, said valvecomprising: a gate valve having a gate that is translated in and out ofa channel of the valve by rotation of a valve handle; and a speedreduction device for reducing a speed at which said valve may be closed,the speed reduction device comprising a gear train with a gear ratiosuch that a number of rotations of said valve handle results in a lessernumber of rotations of a screw that translates said gate with respect tosaid channel; wherein threads on the screw supporting the gate arereversed such that, when the gear train reversed a direction of rotationof the valve handle as applied the screw, a clockwise rotation of thehandle will close the gate and a counter-clockwise rotation of thehandle will open the gate.
 2. A method of preventing water hammer, themethod comprising: closing a valve at a fire hydrant after extractingwater from said fire hydrant, the valve comprising a gate valve having agate that is translated in and out of a channel of the valve by rotationof a valve handle, and closing the valve comprising rotating the valvehandle in a clockwise direction; wherein the valve comprising a speedreduction device that increases an amount of time needed for closingsaid valve, and operating said valve to close said valve comprisesoperating a speed reduction device such that said increased amount oftime needed for closing said valve prevents an occurrence of waterhammer associated with said closing of said valve; wherein the speedreduction device for reducing a speed at which said valve may be closedcomprising a gear train with a gear ratio such that a number ofrotations of said valve handle results in a lesser number of rotationsof a screw that translates said gate with respect to said channel;wherein threads on the screw supporting the gate are reversed such that,when the gear train reverses a direction of rotation of the valve handleas applied to the screw, a clockwise rotation of the handle will closethe gate and a counter-clockwise rotation of the handle will open thegate.